Lidar

Abstract

The application provides a laser radar, comprising: a light emitting unit for emitting a probe light signal; a light receiving unit for receiving a return light signal generated by the probe light signal; a main optical system arranged between the light emitting unit and the light receiving unit, for receiving the probe light signal and transmitting outward, and for receiving the return light signal and transmitting to the light receiving unit; and a beam expanding unit arranged between the main optical system and the light receiving unit, for receiving the return light signal passing through the main optical system and transmitting to the light receiving unit after beam expansion; wherein the equivalent focal length of the combination of the main optical system and the beam expanding unit is greater than the focal length of the main optical system, so as to compress the field angle of the light receiving unit. The laser radar of the application compresses the field angle of the receiving end by extending the focal length of the receiving end through the optical system, without the need of a diaphragm or other devices, and cooperates with the optical system of the same axis to make the structure more compact.

Description

Technical Field

[0001] This invention relates to the field of optical ranging, and more particularly to lidar. Background Technology

[0002] LiDAR (LiDAR) is a detection device that calculates the distance to an object by emitting a laser and detecting the echo signal reflected after the laser reaches the object's surface. Ranging performance is a crucial technical indicator for LiDAR, primarily dependent on the signal-to-noise ratio (SNR) of the system. Ambient light is a significant source of noise affecting the SNR of LiDAR; therefore, reducing ambient light has always been a critical aspect of LiDAR optical system design.

[0003] Current lidar optical systems suppress ambient light primarily through two methods:

[0004] On the one hand, it is necessary to set a suitable focal length for the optical system of the receiver (i.e., the detector side). Specifically, this is because the focal length of the receiver's optical system needs to match the transmitting focal length, the laser, and the effective size of the photodetector. Furthermore, the length of the optical system's focal length has a significant impact on the overall size of the lidar. Therefore, whether it is mechanical or solid-state lidar, most current receiver optical systems have a focal length of less than 100mm.

[0005] For example, silicon photomultiplier tubes (SiPMs) are prone to saturation under strong ambient light conditions. It is typically necessary to limit the field of view of SiPMs to avoid receiving more ambient light. However, this presents a contradiction. For instance, in the receiver optical system, using a large detector while compressing it to a small field of view requires a long focal length optical system; however, using a long focal length optical system is not conducive to achieving a compact and small-sized lidar.

[0006] according to Figure 1 To explain, Figure 1 The height of detector 101 shown is L, f is the focal length of receiving lens 102 (equivalent to a convex lens), and θ is the field of view. It should be noted that the field of view here is the instantaneous field of view (IFOV), which refers to the angle of light received or the field of view of a single photodetector. The formula for calculating the field of view can be obtained as follows: As can be seen from the formula, if a detector 101 with a large photosensitive surface is used (such as when using SiPM), the height L will be relatively large. In order to limit the field of view θ of the detector 101 and avoid receiving more ambient light and causing the detector 101 to saturate, it is necessary to increase the focal length f of the receiver optical system.

[0007] To solve this problem, such as Figure 2As shown, existing technologies suppress ambient light by adding an aperture stop 203 to the optical system at the receiving end. Specifically, as shown in the figure, an aperture stop 203 is placed between the receiving lens 202 and the detector 201. The aperture stop 203 is located at the focal point of the receiving lens 202, and the light passing through the aperture stop 203 covers the entire effective area of ​​the detector 201 (the coverage height L is used as an example in the figure). As can be seen from the figure, the aperture stop 203 allows light within its corresponding field of view θ' to pass through, while blocking light from other field of view angles. This compresses the actual field of view of the detector 201 from θ to θ', and the aperture stop 203 ensures that the passing light covers the entire effective area of ​​the detector 201, thus achieving the effect of a long focal length optical system.

[0008] However, for lidar, the aperture stop is an additional optical component that needs to be added, which increases both the cost and the installation and debugging work.

[0009] On the other hand, some systems use filters corresponding to the laser wavelength to filter ambient light outside the laser wavelength by compressing the filter bandwidth. However, the filter bandwidth is affected by factors such as the laser bandwidth and the operating temperature. For most current lidar systems that use semiconductor lasers as their light source, the space for further compression of the filter bandwidth is relatively limited, and ambient light cannot still be controlled to an ideal level. Summary of the Invention

[0010] In view of the shortcomings of the prior art described above, the present invention provides a lidar that suppresses the influence of ambient light on the detector, improves the dynamic range of lidar detection, and enhances the ranging capability of lidar.

[0011] To achieve the above and other related objectives, a first aspect of the present invention provides a lidar, comprising: an optical emitting unit for emitting a probe optical signal; an optical receiving unit for receiving an echo optical signal generated by the probe optical signal; a main optical system disposed between the optical emitting unit and the optical receiving unit for receiving the probe optical signal and transmitting it outward; and for receiving the echo optical signal and transmitting it to the optical receiving unit; and a beam expander unit disposed between the main optical system and the optical receiving unit for receiving the echo optical signal passing through the main optical system and transmitting it to the optical receiving unit after beam expansion; wherein the equivalent focal length of the combination of the main optical system and the beam expander unit is greater than the focal length of the main optical system, so as to compress the field of view of the optical receiving unit.

[0012] In an embodiment of the first aspect, the transmission path of the probe optical signal in the lidar is partially the same as the transmission path of the echo optical signal.

[0013] In an embodiment of the first aspect, the main optical system includes: a positive lens unit and a beam splitter unit; the positive lens unit is configured to receive the probe light signal from the beam splitter unit and transmit it outward; and to receive the echo light signal and transmit it to the beam splitter unit; the beam splitter unit is configured to receive the probe light signal and transmit it to the positive lens unit; and to receive the echo light signal from the positive lens unit and transmit it to the light receiving unit.

[0014] In an embodiment of the first aspect, the distance between the beam expander and the positive lens unit is less than the focal length of the positive lens unit.

[0015] In an embodiment of the first aspect, the photosensitive surface of the light receiving unit is located at the focal plane of the combination of the main optical system and the beam expander unit.

[0016] In an embodiment of the first aspect, the equivalent focal length is also greater than the distance between the principal plane of the main optical system and the photosensitive surface of the light receiving unit.

[0017] In an embodiment of the first aspect, the beam splitting unit includes: a reflecting unit, including a reflecting portion for reflecting one of the echo light signal and the probe light signal; the reflecting unit further includes a transmitting portion or the reflecting unit is fitted with an external gap to allow the other of the probe light signal and the echo light signal to pass through.

[0018] In an embodiment of the first aspect, the main optical system further includes: a polarization unit disposed on the side of the positive lens unit facing away from the beam splitter unit, for changing the polarization state of the probe light signal and the echo light signal, so that the output probe light signal is in a first polarization state and the output echo light signal is in a second polarization state, the first polarization state being different from the second polarization state; the beam splitter unit disposed between the positive lens unit and the beam expander unit, configured to allow the echo light signal in the second polarization state to pass through.

[0019] In an embodiment of the first aspect, the lidar further includes: a scanning unit, which can be rotatably configured in one or two dimensions, for rotating to a predetermined posture to transmit the detection light signal outward at a corresponding scanning angle, and for transmitting the echo light signal corresponding to the detection light signal to the main optical system.

[0020] In an embodiment of the first aspect, the optical receiving unit includes: an array of photodetectors; the beam expanding unit includes an array of sub-beam expanding units, wherein each sub-beam expanding unit corresponds to one or more photodetectors.

[0021] In an embodiment of the first aspect, the photodetector corresponding to each first sub-beam expander in the central region of the sub-beam expander array corresponds to the center field-of-view angle of the lidar's field of view, and each first sub-beam expander includes a non-eccentric lens; the photodetector corresponding to each second sub-beam expander in the peripheral region outside the central region of the sub-beam expander array corresponds to the edge field-of-view angle outside the center field-of-view angle of the lidar, and each second sub-beam expander includes an eccentric lens.

[0022] In an embodiment of the first aspect, the sub-beam expander array is a microlens array for encapsulating a photodetector array.

[0023] In an embodiment of the first aspect, the photodetector array includes: a circuit board having a first surface on which the photodetector array is disposed; and an optical carrier having a second surface on which the microlens array is disposed, being integrally packaged with the circuit board and having the second surface opposite to the first surface, such that each microlens is disposed corresponding to each photodetector.

[0024] In an embodiment of the first aspect, the light receiving unit includes: a plurality of photodetector arrays, each photodetector array being arranged in a linear array; the beam expanding unit includes at least one cylindrical negative lens, the cylindrical negative lens being disposed corresponding to some or all of the photodetector arrays in the light receiving unit, and the extending direction of the cylindrical negative lens being the length direction of the photodetector array.

[0025] The lidar in this embodiment of the invention achieves the following beneficial effects:

[0026] A long focal length optical system is achieved by combining a main optical system and a beam expander unit. When applied to lidar, this system can achieve a relatively long focal length for the light receiving unit within a relatively compact volume.

[0027] On the one hand, long focal length optical systems can significantly reduce the impact of ambient light on detectors when using detectors with larger photosensitive surfaces (such as SiPM), while still maintaining the compact structure of lidar.

[0028] On the other hand, under the same angular resolution, using a detector with a larger photosensitive surface area (such as a SiPM) allows for a greater number of photosensitive units, thereby improving the dynamic range of the detection system. Therefore, the optical system in the embodiments of the present invention plays a crucial role in the ranging performance of lidar, whether by reducing the influence of ambient light or improving the dynamic range. Attached Figure Description

[0029] Figure 1 This example illustrates the relationship between detector size, field of view, and focal length.

[0030] Figure 2 This example demonstrates a schematic diagram of a lidar system that uses an aperture stop to suppress ambient light.

[0031] Figure 3 A schematic diagram of the optical system of a lidar according to an embodiment of the present invention is shown.

[0032] Figure 4 A schematic diagram of the optical system in an embodiment of the present invention is shown.

[0033] Figure 5A and Figure 5B The following are schematic diagrams of the optical systems of two-dimensional scanning lidar based on polarization beam splitting units in different embodiments of the present invention.

[0034] Figure 6 and Figure 7 The following are schematic diagrams of the optical systems of two-dimensional scanning lidar based on reflection units to achieve beam splitting in different embodiments of the present invention.

[0035] Figure 8A A schematic diagram of the structure implemented by the combination of positive and negative lenses in another embodiment of the present invention is shown.

[0036] Figure 8B exhibit Figure 8A A schematic diagram of the three-dimensional structure of the positive-negative lens combination.

[0037] Figure 9A This diagram illustrates a structural schematic of one arrangement of the photodetector array in an embodiment of the present invention.

[0038] Figure 9B This is a schematic diagram illustrating another arrangement of the photodetector array in an embodiment of the present invention.

[0039] Figure 10 This diagram illustrates the arrangement of the negative lens array and the photodetector array in an embodiment of the present invention.

[0040] Figure 11A and Figure 11B The following are schematic diagrams of optical systems using negative lens arrays as beam expanders in different embodiments of the present invention.

[0041] Figure 12A and Figure 12B The diagrams show the structural schematics of the negative lens array adapted to the photodetector array in different embodiments of the present invention.

[0042] Figure 13 This diagram illustrates the structure of the photodetector array and microlens array package in an embodiment of the present invention. Detailed Implementation

[0043] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and application systems without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0044] The present invention will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can readily implement it. The present invention can be embodied in many different forms and is not limited to the embodiments described herein.

[0045] To clearly illustrate the present invention, components unrelated to the description are omitted, and the same or similar constituent elements throughout the specification are given the same reference numerals.

[0046] Throughout this specification, when it is said that a device is "connected" to another device, this includes not only "direct connection" but also "indirect connection" by placing other components in between. Furthermore, when it is said that a device "comprises" a certain constituent element, unless otherwise stated otherwise, this does not exclude other constituent elements, but rather implies that other constituent elements may be included.

[0047] When we say that a device is "above" another device, this can mean that it is directly above the other device, or it can mean that other devices are present in between. Conversely, when we say that a device is "directly" "above" another device, there are no other devices present in between.

[0048] Although the terms first, second, etc., are used in some instances herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, descriptions such as first interface and second interface, etc. Furthermore, as used herein, the singular forms “a,” “an,” and “the” are intended to also include the plural forms unless the context indicates otherwise. It should be further understood that the terms “comprising,” “including,” indicate the presence of the stated feature, step, operation, element, component, item, kind, and / or group, but do not exclude the presence, occurrence, or addition of one or more other features, steps, operations, elements, components, items, kinds, and / or groups. The terms “or” and “and / or” as used herein are interpreted as inclusive, or mean any one or any combination thereof. Thus, “A, B, or C” or “A, B, and / or C” means “any one of: A; B; C; A and B; A and C; B and C; A, B, and C.” Exceptions to this definition occur only when combinations of elements, functions, steps, or operations are inherently mutually exclusive in some way.

[0049] The technical terms used herein are for reference only to specific embodiments and are not intended to limit the invention. The singular form used herein includes the plural form unless the statement explicitly indicates otherwise. The word "comprising" as used in this specification means to specify a particular characteristic, region, integer, step, operation, element, and / or component, and does not exclude the presence or addition of other characteristics, regions, integers, steps, operations, elements, and / or components.

[0050] Terms such as "below" and "above" indicating relative space are used to more easily explain the relationship of one device relative to another in the accompanying drawings. These terms refer not only to their meaning as shown in the drawings but also to other meanings or operations of the device in use. For example, if the device in the drawings is flipped, a device previously described as "below" another device may now be described as "above" another device. Therefore, the exemplary term "below" encompasses both above and below. The device may be rotated 90° or other angles, and the terms representing relative space are interpreted accordingly.

[0051] Although not explicitly defined, all terms, including technical and scientific terms used herein, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries shall be further interpreted as having a meaning consistent with relevant technical literature and the content of this present instruction, and shall not be over-interpreted as having an ideal or overly formulaic meaning unless otherwise defined.

[0052] LiDAR optical systems suffer from ambient light interference, especially when considering ranging capabilities. Larger photodetectors (e.g., SiPMs) are often chosen, resulting in a wider field of view and thus receiving interference from more angles of ambient light. Current LiDAR systems have implemented improvements to suppress ambient light, but the size of the product limits the ability to achieve a suitable focal length, necessitating the addition of aperture stops and other optical components to extend the focal length. Another approach is to compress the photodetector's field of view by reducing the bandwidth of the filter, but this is limited by the physical configuration parameters of the LiDAR system.

[0053] Therefore, an improved lidar structure is provided in this embodiment of the invention.

[0054] like Figure 3 The diagram shows a schematic representation of the optical system of a lidar according to an embodiment of the present invention. The lidar 300 includes: a light emitting unit 301, a light receiving unit 302, a main optical system 303, and a beam expander unit 304.

[0055] The optical emitting unit 301 is used to emit a probe optical signal and can also be referred to as a transmitter. In some embodiments, the optical emitting unit 301 may include an optical emitter array, which contains multiple optical emitters arranged in a two-dimensional planar array or a one-dimensional linear array. Each optical emitter may be an edge-emitting semiconductor laser (EEL) or a vertical-cavity surface-emitting laser (VCSEL).

[0056] The light receiving unit 302 is used to receive the echo light signal generated by the probe light signal. The probe light signal can illuminate the surface of an obstacle and reflect to form the echo light signal. The light receiving unit 302 can also be referred to as a receiving end. In some embodiments, the light receiving unit 302 may include a photodetector array, which includes multiple photodetectors arranged in a two-dimensional planar array or a one-dimensional linear array. Each photodetector can be a silicon photomultiplier tube (SiPM) or a single-photon avalanche diode (SPAD), etc.

[0057] The main optical system 303 is configured between the light emitting unit 301 and the light receiving unit 302, and is used to receive the probe light signal and transmit it outward; and to receive the echo light signal and transmit it to the light receiving unit 302.

[0058] In the diagram, the first transmission path J of the probe light signal is partially the same as the second transmission path K of the echo light signal, meaning that the main optical system 303 is a coaxial optical system for transmitting and receiving. The main optical system 303 includes a positive lens unit 331 and a beam splitter unit 332. The beam transmission path between the positive lens unit 331 and the beam splitter unit 332 is shared by the first transmission path J and the second transmission path K, where J is indicated by a thin black solid line arrow and K is indicated by a thicker shaded arrow.

[0059] The positive lens unit 331 is used to receive the probe light signal from the beam splitter unit 332 and transmit it outward from the lidar 300, and to receive the echo light signal and transmit it outward from the beam splitter unit 332. Specifically, the positive lens unit 331 can converge the received probe light signal for collimation before transmitting it outward, specifically, as shown in the figure, outputting it to the scanning unit 305 and transmitting it outward from the lidar 300 via the scanning unit 305; furthermore, the positive lens unit 331 can also converge the echo light signal and transmit it to the light receiving unit 302, specifically, as shown in the figure, receiving the echo light signal from the scanning unit 305. In some examples, the scanning unit 305 can be rotatably configured in one or two dimensions, used to rotate to a predetermined posture so that the probe light signal is transmitted outward at a corresponding scanning angle, and used to transmit the echo light signal corresponding to the probe light signal to the main optical system 303. Exemplarily, the scanning unit 305 can include any one of a galvanometer, a MEMS mirror, or a rotating mirror.

[0060] The beam splitter 332 enables the transmission of the probe light signal and the echo light signal between the light emitting unit 301, the light receiving unit 302, and the positive lens unit 331. Figure 4 As shown, on one hand, the probe light signal is transmitted along the first transmission path J indicated by the thinner black solid arrow, and the beam splitter 332 receives the probe light signal from the light emitting unit 301 and transmits it to the positive lens unit 331; on the other hand, the echo light signal is transmitted along the second transmission path K indicated by the thicker shaded arrow, and the beam splitter 332 receives the echo light signal from the positive lens unit 331 and transmits it to the light receiving unit 302. Exemplarily, the beam splitter 332 can split the probe light signal and the echo light signal by deflection or transmission. For example, in... Figure 4 In this example, the beam splitter 332 allows the echo light signal to pass through while deflecting (e.g., reflecting) the probe light signal before transmission. In other embodiments, the optical system may also be configured so that the beam splitter 332 deflects the received echo light signal before transmission while allowing the received probe light signal to pass through.

[0061] The beam expander unit 304 is disposed between the main optical system 303 and the light receiving unit 302, and is used to receive the echo light signal passing through the main optical system 303 and transmit it to the light receiving unit 302 after beam expansion. In a specific example, the beam expander unit 304 corresponds to Figure 3 The negative lens unit in the embodiment can be implemented as a negative lens or a group of negative lenses. Through the combined action of the positive lens unit 331 and the negative lens unit, the focal length of the receiving optical system in the lidar 300 is lengthened.

[0062] In some embodiments, the beam splitter 332 may be an optical component that allows light signals of a specific polarization state to pass through, while light signals of other polarization states are blocked. In a specific example, the probe light signal and the echo light signal can be made to have different polarization states, so that the beam splitter 332 allows the echo light signal of a specific polarization state to pass through, while preventing the probe light signal of other polarization states from passing through.

[0063] To ensure that the probe light signal and the echo light signal are in different polarization states, in a possible example, the main optical system 303 further includes a polarization unit disposed on the side of the positive lens unit 331 facing away from the beam splitter unit 332, for changing the polarization states of the probe light signal and the echo light signal, so that the output probe light signal is in a first polarization state and the output echo light signal is in a second polarization state, the first polarization state being different from the second polarization state; correspondingly, the beam splitter unit 332 is disposed between the positive lens unit 331 and the beam expander unit 304, configured to allow the echo light signal in the second polarization state to pass through.

[0064] In some other embodiments, the beam splitting unit 332 can also be implemented by a reflection unit. The reflection unit may include a reflective portion for reflecting one of the echo light signal and the probe light signal, and the reflection unit may also include a transmission portion (see details). Figure 7 (Example) or the reflective unit is fitted with an external gap (see details). Figure 6 (Example) to allow the other of the probe optical signal and the echo optical signal to pass through, for example, by transmission.

[0065] The following section will explain the principle of how the positive lens unit 303 and the beam expander unit 304 work together to realize a long focal length optical system from the perspective of optical path structure.

[0066] It should be noted that the following Figure 4 , Figure 5A , Figure 5B , Figure 6 , Figure 7 The field of view shown in the embodiments is the instantaneous field of view, that is, the principle of the technical solution of the present invention is explained more clearly and intuitively by using the light-receiving angle or observation field of a single photodetector.

[0067] like Figure 4 The diagram shows a structural schematic of an optical system according to an embodiment of the present invention. Figure 4 The optical system described herein can be applied to the receiving end of a lidar system. Specifically, the optical system includes a combination of a positive lens 401 and a negative lens 402. The positive lens 401 has a focal length of f1, a field of view of α, and a focal point of A. The negative lens 402 has a field of view of γ. Light rays passing through the positive lens 401 should converge at point A. However, after the negative lens 402 is placed between the principal plane of the positive lens 401 and its focal point A, the converging point of the light rays shifts from A to point B due to the dilatation effect of the negative lens 402, and the field of view becomes γ, which is less than α. The distance between the principal plane of the equivalent lens formed by the combination of the positive lens 401 and the negative lens 402 and the converging point B is f, which is equivalent to the focal length of the equivalent lens being f.

[0068] It can be observed that f is longer than f1. When the distance between the positive lens 401 and the negative lens 402 is constant (for example, the distance between their principal planes is less than the focal length of the positive lens 401), the focal length of the optical system can be increased by combining the positive lens 401 and the negative lens 402.

[0069] Furthermore, if the photodetector is set on the focal plane where point B is located, then the distance L between the principal plane of the positive lens 401 and the focal plane where point B is located is the physical length of this optical system. Since f is greater than L, it indicates that the equivalent focal length f of the equivalent lens exceeds the limitation of the physical size of the optical system.

[0070] It should be noted that the positive lens 401 and negative lens 402 in the figure are only simplified representations. In practical applications, they can be equivalent representations of a lens group and are not limited to the figure.

[0071] Clearly, this optical system can effectively extend the focal length to a point beyond the physical size limit, while maintaining the compact structure of the lidar, thus effectively solving the problems in the existing technology and eliminating the need for an aperture stop.

[0072] When this optical system is applied to lidar, the existing optical system on the receiver side of the lidar already includes a lens group for focusing the echo light signal, corresponding to... Figure 4 The positive lens 401 is used in this process. Therefore, by simply placing a negative lens 402 or a lens group that implements the negative lens 402 between this lens group and the photodetector, the focal length at the receiving end can be significantly extended. This allows for the use of larger photodetectors (such as SiPMs, which have more than twice the photosensitive surface of APDs) according to... f can increase with L, limiting the field of view angle γ to suppress interference from ambient light, thereby avoiding saturation of the photodetector.

[0073] In some alternative embodiments, it is also possible to... Figure 4 By adding optical path deflection structures (such as adding reflectors) to the basic structure, the system size L = f1 can be made so that the structure remains compact and a longer focal length f can be achieved while keeping the physical size of the optical system at the receiving end of the lidar unchanged.

[0074] In possible examples, such as Figure 5A and Figure 5B The figures show schematic diagrams of the optical systems of two-dimensional scanning lidars that achieve beam splitting based on polarization beam splitting units in different embodiments of the present invention.

[0075] The lidar includes: a light emitter array 501, a photodetector array 502, a positive lens 503 (equivalent representation, which can be implemented by a lens group), a negative lens 504 (equivalent representation, which can be implemented by a lens group), a polarization beam splitter, a quarter-wave plate 506, a reflector 507, and a scanner 508. Figure 5A and Figure 5B The example is in Figure 4 In a specific implementation example based on the embodiment, the light emitter array 501 and the photodetector array 502 respectively correspond to Figure 4 An example implementation of the light emitting unit and light receiving unit in the embodiment. The positive lens 503 and negative lens 504 respectively correspond to... Figure 4 Example implementations of positive lens unit 503 and negative lens unit 504 in [the document / concept]. Figure 5A and Figure 5B The simplified diagrams of the positive lens 503 and negative lens 504 are used to represent this. The polarization beam splitter corresponds to... Figure 4 An example implementation of the beam-splitting unit in the embodiment, corresponding to the quarter-wave plate 506. Figure 4 In this embodiment, the polarization unit, quarter-wave plate 506, can be used to change the polarization state of the transmitted light signal. Scanner 508 corresponds to... Figure 4 Example implementation of the scanning unit.

[0076] Figure 5A and Figure 5B The main difference is that, Figure 5A The polarization beam splitter in the design is implemented as a 505A polarization beam splitter prism. Figure 5B The polarization beam splitter in the design is implemented as a 505B polarization beam splitter.

[0077] Specifically, in Figure 5A and Figure 5BIn this embodiment, the light emitter array 501 emits a laser beam. Part of the polarized light is reflected by a polarization beam splitter, collimated by a positive lens 503, and then changed to a first polarization state by a quarter-wave plate 506. After being reflected by a mirror 507, it is scanned by a scanner 508 and illuminates the target in the corresponding field of view. The target reflects the laser beam, forming an echo signal. The echo signal returns to the lidar, is reflected by the scanner 508 and the mirror 507, and after passing through the quarter-wave plate 506, its polarization state is changed again to a second polarization state. After being converged by the positive lens 503, part of the polarized light is transmitted by the polarization beam splitter, and then extended by the negative lens 504, before being received by the detector array 502. The mirror 507 is used to fold the optical path, making the overall optical path structure more compact, but it is not a necessary component. For example, the mirror 507 can be omitted, and the beam whose polarization state has changed after passing through the quarter-wave plate 506 can be directly scanned by the scanner 508.

[0078] In a possible embodiment, the negative lens may be a single lens or multiple lenses arranged back and forth along the optical path to further extend the focal length.

[0079] In a specific embodiment, based on the optical path system shown in the above embodiments, the receiver end, through an optical system using a combination of positive and negative lenses, can achieve a focal length range of, for example, 100mm-300mm. The transmitter and receiver ends of the lidar can share the positive lens, while the polarization beam splitter is located between the positive and negative lenses. The negative lens is located separately at the receiver end and is set in relation to the photodetector array, thus realizing a long focal length receiver optical system.

[0080] In optional examples, the transmitter can be equipped with a relatively short focal length optical system to ensure effective laser emission; while the receiver can be equipped with a relatively long focal length optical system. This allows the use of a photodetector with a larger photosensitive surface (such as a SiPM detector) for reception. Thus, the SiPM has a smaller field of view, correspondingly receiving less ambient light. Simultaneously, with the same angular resolution, using a larger photosensitive surface allows for a greater number of photosensitive units, thereby improving the dynamic range of the lidar.

[0081] LiDAR can employ either a light emitter array or a photodetector array. The photodetector array can be positioned on the focal plane of the optical system, meaning the photosensitive surface of the photodetector array is located at the focal plane of the main optical system combined with the beam expander. The light emitter array and photodetector array can be one-dimensional linear arrays or two-dimensional planar arrays. Two-dimensional planar arrays can be arranged in a matrix or in a multi-column staggered arrangement. One or more light emitters and one or more corresponding photodetectors form a detection channel. Within the same detection channel, the light emitters and photodetectors transmit detection light signals and receive the resulting echo light signals.

[0082] In some embodiments, during lidar operation, the light emitter array and photodetector array can emit light column by column, one by one, through their respective detection channels. In one example, the columns can emit light in a rotating fashion, meaning that once one column finishes emitting light, the light emitters of each detection channel in the next column emit light sequentially. Alternatively, in another example, each column of linear arrays can emit light simultaneously, meaning the first channel of each column's linear array emits light simultaneously, followed by the other detection channels in each column emitting light sequentially according to the column's arrangement. Yet another example allows corresponding detection channels of multiple linear arrays within the same column to emit light simultaneously. For instance, the first detection channels of multiple linear arrays within the same column emit light simultaneously, followed by the other detection channels in the column's arrangement, and so on. After multiple linear arrays in the same column have finished emitting light, they emit light in a rotating fashion, meaning that once multiple linear arrays in one column have finished emitting light, the next column's multiple linear arrays emit light according to the above process. Each photodetector in the photodetector array also operates in conjunction with the light emitter of the same detection channel to receive the corresponding echo light signal according to any of the above methods.

[0083] It should be noted that in other embodiments, the light emitting unit may also be implemented as a single laser, and the light receiving unit may also be implemented as a single photodetector, etc., and is not limited to the above.

[0084] In other embodiments, besides the beam splitting based on a polarization beam splitter as described above, the beam splitter can also be implemented using a reflection unit. This reflection unit has a reflective portion for reflecting one of the probe light signal and the echo light signal, and may have a transmission portion or cooperate with an external gap to transmit the other of the probe light signal and the echo light signal, thereby achieving beam splitting. Furthermore, the aforementioned positive-negative lens combination can also be used to extend the focal length of the receiving end.

[0085] like Figure 6 and Figure 7 The figures show schematic diagrams of the optical systems of two-dimensional scanning lidars that achieve beam splitting based on reflection units in different embodiments of the present invention.

[0086] like Figure 6 and Figure 7 As shown, the lidar includes: a light emitter array 601, a photodetector array 602, a positive lens 603, a negative lens 604, a reflecting unit, a reflecting mirror 606, and a scanner 607. It should be noted that the positive lens 603 and the negative lens 604 are still equivalent representations.

[0087] Figure 6 and Figure 7 The differences between the embodiments lie in the implementation of the reflection unit and the corresponding changes in the positions of the transmitting and receiving ends.

[0088] and Figure 5A and Figure 5B The difference is that, Figure 6 The reflecting unit in the image is implemented as a reflecting mirror 605A, which is relatively smaller in size than the positive lens 603. Figure 7 The reflective unit in the design is implemented as a pinhole mirror 605B.

[0089] Figure 6 The detection light signal output by the light transmitter array 601 is reflected by the reflector 605A to the positive lens 603. After being collimated by the positive lens 603, it is reflected by the reflector 606 to the scanner 607. After being reflected by the scanner 607, it is emitted out of the lidar. The corresponding echo light signal enters the lidar and is reflected by the scanner 607 and the reflector 606 to the positive lens 603. The positive lens 603 converges the echo light signal, and the echo light signal is transmitted through the gaps around the reflector 605A to the negative lens 604. After being incident on the photodetector array 602 by the negative lens 604, it is emitted into the photodetector array 602.

[0090] Figure 7 The detection light signal output by the light transmitter array 601 passes through the small hole in the center of the pinhole reflector 605B, and exits through the positive lens 603, reflector 606, and scanner 607; the corresponding echo light signal enters the lidar, passes through the scanner 607, reflector 606, positive lens 603, and pinhole reflector 605B, is reflected by pinhole reflector 605B to the negative lens 604, and is then transmitted to the photodetector array 602. It should be noted that... Figure 7 In one embodiment, the transmissive portion of the reflector is a small hole to allow light to pass through; in other embodiments, the transmissive portion may also be of other shapes and is not limited to a small hole; or the transmissive portion may also be implemented in other forms, such as transparent glass.

[0091] The implementation of positive and negative lenses in a positive-negative lens combination can be selected.

[0092] In some embodiments, the positive lens can be implemented as a biconvex lens, and the negative lens can be implemented as a biconcave lens.

[0093] In some other embodiments, the positive lens may be a biconvex lens, and the negative lens may be a cylindrical negative lens. For example... Figure 8A and Figure 8B As shown, the cylindrical negative lens combined with the positive lens 801 can be a plano-concave cylindrical lens 802. Figure 8B yes Figure 8A A three-dimensional view is provided to facilitate understanding of its structure. By employing a cylindrical negative lens, the combination of positive and negative lenses can maintain a short focal length in one direction (e.g., Figure 8B As shown in the Y direction (i.e., the extension direction of the cylindrical negative lens), while a long focal length is achieved in the other direction (e.g.) Figure 8BIn the Z-direction, the long focal length is achieved by utilizing the concave surface of the cylindrical negative lens in the Z-direction. It should be noted that in other embodiments, the cylindrical negative lens may also be a biconcave cylindrical negative lens, and is not limited to this embodiment.

[0094] Because the arrangement of light-receiving units, such as photodetector arrays, can be non-centrosymmetric—meaning the number, size, and arrangement of detectors may differ in different directions—the aforementioned cylindrical negative lens scheme is suitable for scenarios where the size of the light-receiving unit is limited. This cylindrical negative lens scheme can be used when the photosensitive surface size of the light-receiving unit is limited in a certain direction, or when a long focal length system is not suitable. For example, Figure 9A In the photodetector array, multiple photodetectors 901 (e.g., SiPM) are arranged at intervals along the length direction.

[0095] However, if the photodetector array is arranged as follows Figure 9B The arrangement of the photodetectors 901 is seamless, forming a long, linear array. The length direction (horizontal axis in the diagram) can be referenced. Figure 8B The Y direction in the figure, or you can refer to Figure 10 , Figure 12A , Figure 12B The direction of the laser radar's echo spot (which can be considered circular) needs to cover as much of the elongated linear array detector as possible. The photodetector array may include: a width direction perpendicular to the stated length direction (see reference...). Figure 8B The multiple elongated linear arrays of photodetectors (arranged along the Z-direction) are described above. The arrangement of photodetectors 901 can be referenced from [reference needed]. Figure 10 The photodetector 1001 is used in multiple rows. It is understandable that... Figure 9B In this system, because the spacing between adjacent photodetectors 901 along the length direction may be very small, increasing the focal length along the length direction can easily lead to crosstalk between the photodetectors 901 in the linear array. Therefore, a long focal length system is not suitable for the length direction. However, in the width direction, the spacing between multiple linear arrays may be larger, and even if the focal length is increased, crosstalk is relatively less likely to occur. Therefore, for example, a longer focal length system can be used... Figure 8A , Figure 8B The cylindrical negative lens scheme in the middle maintains the focal length in the length direction and achieves a long focal length in the width direction, suppressing ambient light and improving the signal-to-noise ratio.

[0096] like Figure 10The diagram illustrates the arrangement of the negative lens array and the photodetector array in an embodiment of the present invention. The photodetector 1001 is shown as square, and each negative lens 1002 in the negative lens array corresponds to one photodetector 1001. The circular area covering each photodetector 1001 in the diagram is a simplified representation of the echo light signal spot 1003. The negative lens 1002 can be a concave microlens. The concave microlens can be an aspherical mirror, specifically a cylindrical negative lens or a general concave lens, or a plano-concave lens or a biconcave lens. As shown in the figure, exemplarily, each negative lens can be respectively set corresponding to each photodetector (such as a SiPM), and each negative lens 1002 can be set separately, as indicated by the dashed box in the figure; or, multiple negative lenses 1002 can also be integrally formed, that is, all (or part) of the negative lenses in the negative lens array are connected to form an optical device, as shown in box 1004 in the figure. The integrated negative lens array optical device can achieve a large field of view (e.g., 10°~20°).

[0097] In some embodiments, aberrations at different field-of-view angles can be corrected by configuring the type of each concave microlens in the negative lens array. Specifically, since edge field-of-view aberrations are greater than central field-of-view aberrations, the concave microlenses in the central region of the negative lens array (corresponding to the central field-of-view angle of the lidar) can be configured as non-eccentric lenses, while the concave microlenses in the peripheral region outside the central region (corresponding to the edge field-of-view angle of the lidar) can be configured as eccentric lenses. Specifically, eccentric lenses can deflect the light beam, causing the beam at the edge positions to bend towards the central region. Therefore, this structure helps to reduce the spacing and size between photodetectors.

[0098] In some embodiments, for each photodetector in the photodetector array, the beam expander unit may include an array of sub-beam expander units, wherein each sub-beam expander unit corresponds to one or more photodetector settings. Exemplarily, the beam expander unit may be a negative lens array, wherein each sub-beam expander unit is a negative lens.

[0099] like Figure 11A and Figure 11B The diagram shows a schematic representation of the optical system using a negative lens array 1102 as a beam expander in different embodiments of the present invention. Figure 11A , Figure 11B The Z-axis and X-axis directions can be aligned with... Figure 8B Consistent with the above.

[0100] like Figure 11AThe diagram illustrates an optical system suitable for a mechanical lidar, specifically a lidar with a rotating structure that rotates during operation. The optical system includes a positive lens 1101 and a negative lens array 1102. Corresponding to the photodetector array 1103, each negative lens 1121 can correspond to one or more photodetectors 1131 to transmit the echo light signal of the corresponding detection channel.

[0101] For example Figure 11B The diagram illustrates an optical system suitable for scanning lidar. The optical system includes a positive lens 1101, a negative lens array 1102, and a scanner 1104. The negative lens array 1102 is positioned corresponding to a photodetector array 1103. The scanner 1104 can rotate in one or two dimensions to select the optical signal transmission for a corresponding detection channel. This embodiment of the optical system can be applied to, for example… Figure 5A , Figure 5B , Figure 6 , Figure 7 In the example.

[0102] from Figure 11A and Figure 11B As can be seen from the embodiments, the optical system of positive-negative lens combination in the embodiments of the present invention can be flexibly applied to different types of lidar to compress the field of view by extending the focal length of the receiver, thereby suppressing ambient light interference. Therefore, this optical system can improve the anti-interference performance of different types of lidar products, thereby achieving the goal of improving the ranging performance of various types of lidar products.

[0103] In some embodiments, the arrangement of the negative lens array can also be adapted to the photodetector array. For example, Figure 12A The structure of a negative lens array 1200A in one embodiment is shown. The negative lens array 1200A can be adapted to include a plurality of strip-shaped concave microlenses 1201A (such as cylindrical concave lenses) arranged continuously along a specific direction. Each concave microlens 1201A can correspondingly cover a row of photodetectors, a photodetector array consisting of a row of several photodetectors, or a row of photodetectors consisting of photodetectors and the photodetector array arranged at intervals. The photodetector array, for example, presents as... Figure 9B In a photodetector array, the spacing between photodetectors in each row, between photodetector arrays, or between photodetectors and photodetector arrays can be minimized. Alternatively, as... Figure 12B As shown, another embodiment illustrates the structure of a negative lens array. The negative lens array 1200B includes a plurality of concave microlenses 1201B spaced apart. Each concave microlens 1201B can cover a photodetector or a photodetector array composed of several photodetectors, for example, presented as... Figure 9B The photodetector array in the middle. Figure 12A and Figure 12BThe structure of the negative lens array can be selected based on the spacing of the photodetectors.

[0104] In some embodiments, the negative lens array is also easily packaged with a photodetector array for alignment with each photodetector. Because its precision is at the millimeter level, it does not significantly affect the effect of elongating the focal length.

[0105] like Figure 13 The diagram shows a schematic representation of the packaging structure of the photodetector array and the microlens array (i.e., an array composed of multiple concave microlenses) in an embodiment of the present invention.

[0106] The figure shows a circuit board 1301 and an optical carrier 1302.

[0107] The circuit board 1301, such as a printed circuit board (PCB), has a first surface on which the photodetector array is disposed. Two columns or two rows of photodetectors 1303 in the photodetector array are shown exemplary in the figure, but their number is not limited thereto. See Figure 8 for reference. Figure 11A , Figure 11B Use the X, Y, and Z directions as a reference. Figure 13 The Z and X directions in the equation.

[0108] The optical carrier 1302 has a second surface on which the microlens array is disposed. The optical carrier is integrally packaged with the circuit board, with the second surface facing the first surface, so that each microlens 1305 (i.e., a microconcave lens) is disposed corresponding to each photodetector 1303, as shown in Figure 11. Figure 12A , Figure 12B The positional correspondence in the text.

[0109] In this embodiment, the circuit board may include a sidewall 1306 protruding from the circuit board 1301 and surrounding the photodetector array. The optical carrier 1302 is connected to the sidewall 1306 to form a cavity accommodating the photodetector array. The circuit board 1301 and the sidewall 1306 can be an integrally formed structure or independent components.

[0110] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A lidar, characterized in that, include: The optical emitting unit is used to emit detection optical signals; An optical receiving unit is used to receive the echo optical signal generated by the probe optical signal; The main optical system includes a positive lens unit disposed between the light emitting unit and the light receiving unit, for receiving the probe light signal and transmitting it outward; and for receiving the echo light signal and transmitting it to the light receiving unit. The beam expander unit, including a negative lens or a negative lens group, is located between the main optical system and the light receiving unit, and the distance between it and the positive lens unit is less than the focal length of the positive lens unit. It is used to receive the echo light signal passing through the main optical system and transmit it to the light receiving unit after beam expansion. The equivalent focal length of the main optical system and the beam expander combined is greater than the focal length of the main optical system and greater than the distance from the main plane of the main optical system to the photosensitive surface of the light receiving unit, so as to compress the field of view of the light receiving unit.

2. The lidar according to claim 1, characterized in that, In lidar, the transmission path of the detection light signal is partially the same as the transmission path of the echo light signal.

3. The lidar according to claim 1, characterized in that, The main optical system includes: a beam-splitting unit; The positive lens unit is used to receive the probe light signal from the beam splitter and transmit it outward; and to receive the echo light signal and transmit it to the beam splitter. The beam splitting unit is used to receive the probe light signal and transmit it to the positive lens unit; and to receive the echo light signal from the positive lens unit and transmit it to the light receiving unit.

4. The lidar according to claim 1, characterized in that, The photosensitive surface of the light receiving unit is located at the focal plane of the combination of the main optical system and the beam expander unit.

5. The lidar according to claim 3, characterized in that, The beam splitting unit includes: a reflection unit, including a reflective part, for reflecting one of the echo optical signal and the probe optical signal; The reflective unit further includes a transmission section or the reflective unit is fitted with an external gap to allow the other of the probe light signal and the echo light signal to pass through.

6. The lidar according to claim 3, characterized in that, The main optical system further includes a polarization unit disposed on the side of the positive lens unit facing away from the beam splitter unit, used to change the polarization state of the probe light signal and the echo light signal so that the output probe light signal is in a first polarization state and the output echo light signal is in a second polarization state, wherein the first polarization state is different from the second polarization state. The beam splitting unit is located between the positive lens unit and the beam expander unit, and is configured to allow the echo light signal of the second polarization state to pass through.

7. The lidar according to claim 1, characterized in that, Also includes: The scanning unit can be rotatably arranged in one or two dimensions, and is used to rotate to a predetermined posture so that the detection light signal is transmitted outward at a corresponding scanning angle, and to transmit the echo light signal corresponding to the detection light signal to the main optical system.

8. The lidar according to claim 1, characterized in that, The optical receiving unit includes an array of photodetectors; the beam expanding unit includes an array of sub-beam expanding units, wherein each sub-beam expanding unit corresponds to one or more photodetectors.

9. The lidar according to claim 8, characterized in that, The photodetectors corresponding to each first sub-beam expander in the central region of the sub-beam expander array correspond to the center field-of-view angle of the lidar's field of view, and each first sub-beam expander includes a non-eccentric lens; the photodetectors corresponding to each second sub-beam expander in the peripheral region outside the central region of the sub-beam expander array correspond to the edge field-of-view angles outside the center field-of-view angle of the lidar, and each second sub-beam expander includes an eccentric lens.

10. The lidar according to claim 8, characterized in that, The sub-beam expander array includes a microlens array for encapsulating the photodetector array.

11. The lidar according to claim 10, characterized in that, The optical receiving unit includes: A circuit board having a first surface on which the photodetector array is disposed; An optical carrier having a second surface on which the microlens array is disposed, is integrally packaged with the circuit board such that the second surface is opposite to the first surface, so that each of the microlenses is disposed corresponding to each of the photodetectors.

12. The lidar according to claim 1, characterized in that, The light receiving unit includes: multiple photodetector arrays, each photodetector array being arranged in a linear array; the beam expanding unit includes at least one cylindrical negative lens, the cylindrical negative lens being disposed corresponding to some or all of the photodetector arrays in the light receiving unit, and the extension direction of the cylindrical negative lens being the length direction of the photodetector array.

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